What the substrate needs to do
Use a clean soil-style substrate for Nhandu carapoensis that can hold its shape without becoming hard, dusty or permanently waterlogged.
For Nhandu carapoensis, the substrate in a Brazilian Red Tarantula enclosure should support normal movement and retreat building. Heavy decor must not be able to collapse if the spider digs underneath it.
Depth
Brazilian Red Tarantulas are terrestrial, so give Nhandu carapoensis enough substrate for normal digging while also keeping the fall distance from the lid low. A stable ground-level hide should sit securely on or in the substrate.
Match substrate depth to the current size of Nhandu carapoensis. Small slings and fossorial individuals often use proportionally more depth than a large settled terrestrial adult.
Moisture
For Brazilian Red Tarantulas, maintain moderate moisture gradient with a water dish and good airflow. Add water in a controlled area and judge how the enclosure changes over several days instead of trying to keep every centimetre equally wet.
Substrate moisture for Nhandu carapoensis should work together with ventilation. Persistent condensation, a stale smell or widespread mould usually means the setup is staying too wet.
Compaction and stability
Press the lower substrate layers firmly enough that a retreat or burrow for Nhandu carapoensis does not collapse immediately. The upper surface can remain looser where appropriate.
For Nhandu carapoensis, keep rocks, heavy cork and ornaments in a Brazilian Red Tarantula enclosure low and secure so excavation cannot undermine them.
When substrate needs replacing
Spot-clean waste and prey remains from the Nhandu carapoensis enclosure. Normal digging, webbing or rearrangement by the spider is not a reason to replace clean substrate.
For Nhandu carapoensis, replace all substrate for a Brazilian Red Tarantula only when it is fouled, contaminated, persistently mouldy or no longer structurally usable.